Pharmacological control of ciliary activity in the young sea urchin larva. Effects of monoaminergic agents.

Ciliary activity is affected by serotonin, dopamine and various alpha- and beta-adrenergic agonists reacting with specific receptors. The effects of various monoamine precursors applied at hatching or later on suggest that the initiation of ciliary activity and its control during early gastrulation reflects a temporary formation of monoamines. Application of monoamines brings about stimulation throughout gastrulation with some exceptions which may reflect side effects or some mechanism of feedback inhibition. Strong stimulation is often followed by conspicuous, transient decrease in ciliary activity around the mid-gastrula stage presumably reflecting feedback inhibition and compensatory mechanisms alleviating this.